This invention relates to improvements in solar energy conversion apparatus. More particularly, it relates to apparatus for making more efficient use of solar energy.
Conventional solar energy conversion systems comprise a linear array of photovoltaic solar cells for directly converting incident solar energy to electrical energy. Typically, such systems make use of relatively large trough reflectors, such as those disclosed in my U.S. Pat. No. 4,119,365, for concentrating sunlight upon the solar cell array. While making much more solar energy available to the solar cells for conversion to electrical power, the large reflectors present several problems to the effective operation of the system. First, the concentrated solar energy produces intense heating of the solar cell array. If this heating is not controlled by active or passive cooling, the solar cell efficiency and lifetime will be significantly reduced. One well-known technique for alleviating the heating problem is to use optical bandpass filters to prevent those optical wavelengths of solar energy to which the solar cell is not responsive from reaching the cell. This approach, however, is very inefficient in that it fails to make use of the solar energy outside the spectral response of the solar cells.
Another problem associated with using large reflectors to concentrate solar energy on a solar cell array is that the large reflectors of the type commonly used in solar energy conversion systems are, by economic necessity, of relatively low optical quality. Hence, they are not capable of providing uniform heating of the cell array and, in fact, tend to produce "hot spots" which accentuate the heating problem and shorten the cell life. Also, due to their imperfection, these reflectors are incapable of focusing all incident radiation on the solar cells. Thus, some of the received solar energy is wasted.